A three-point seat belt device employing webbing is used as a typical seat belt device for holding a vehicle occupant or the like safely in a seat. In this type of seat belt device, one end portion of the webbing is latched to a retractor and another end portion is latched to a lap anchor fixed to a vehicle body via a through anchor. By engaging a through tongue disposed in an intermediate portion of the webbing between the lap anchor and the through anchor with a buckle device fixed to a vehicle body inner side, the occupant is restrained in the seat.
The buckle device is normally constituted by an anchor plate that can be attached to the vehicle body side, a buckle to which the tongue of the seat belt can be detachably attached, and a connecting member that connects the anchor plate to the buckle (see Patent Document 1, for example).
Patent Document 1: Japanese Utility Model Application Publication No. 1-117963
Incidentally, when a buckle device is used in a rear seat of an automobile, the buckle device preferably possesses a predetermined rigidity that enables the buckle to stand by itself relative to the anchor plate but does not cause an obstruction to a boarding/alighting occupant.